1. Field of the Invention
The invention pertains to the field of sound transducers. More particularly, the invention pertains to earphones for communications devices.
2. Description of Related Art
It is well documented in literature that the use of double hearing protection (earmuff and earplug) is superior in providing noise attenuation compared to using only one hearing protection device alone. Often communications are also necessary, and thus, a communications earplug is used.
U.S. Pat. No. 4,972,491, “Ear-Mic Headseat/Eardefender” shows such an arrangement where earplugs within earmuffs/headset are hard-wired to headset cord. This is discussed in the June, 2000, issue of the Journal of the Audio Engineering Society in an article entitled “Development of the Wireless Communications Earplug for Application in Military Aviation (Van Wijngaarden et al, J. Audio Eng. Soc., Vol. 48, No. 6, pp. 553-558).
The problem with typical communications earplugs is that they employ wires to provide the communications signal, and the problems with using wires are manifold.
Inductive coupling for communications is known to the art. For example, see U.S. Pat. No. 2,268,665, “Method and Arrangement for Transferring Telephone Conversations to Other Electrical Devices” which is a cradle for telephone handset which picks up sound by inductance, or U.S. Pat. No. 3,322,897, “Coil Pick-up and Tube Recorder System” which uses circular loop pickup around handset earpiece to pick up telephone signals for a recorder.
Inductive coupling is commonly used between a telephone handset and a hearing aid. This application is often referred to as a “T-coil”. For examples, see U.S. Pat. No. 2,530,621, “Wearable Hearing Aid with Inductive Pick-Up for Telephone Reception”, or U.S. Pat. No. 5,796,821, “Hearing aid telephone interconnect system”.
U.S. Pat. No. 3,125,646, “Electromagnetically Coupled Hearing Aid” couples an amplified signal from a sound input unit in eyeglasses or headband to a sound output unit in user's ear.
U.S. Pat. No. 5,420,930, “Hearing aid device” uses a receiver assembly having a flexible coil shape worn in the outer portion of the auditory canal with a small transducer that extends into the auditory canal, and a transmitter assembly. The receiver is driven by magnetic induction from the transmitter assembly positioned a few inches away, as in a neck pendant. Similarly, in U.S. Pat. No. 6,208,740, “Stereophonic magnetic induction sound system” the user wears a necklace with transmitter which transmits sound inductively to active receiver units in ears.
US Published Patent Application 2004/151,334, “Actuator for an active noise control system” is an in-ear transducer for use in ANR system with several embodiments, all including permanent magnets, diaphragms and voice coils.
US Published Patent Application 2005/18,859, “Optically Driven Audio System” shows an alternate system of earmuffs/in-ear earplug using optical transmission from transmitters to active receivers.